Inkjet printing systems form printed images by ejecting print fluids onto various print media. Printheads are controlled to eject individual drops of print fluid from nozzles onto print media at particular locations to form images such as graphics and text on the media. Print fluids can include ink and other fluids, such as treatment fluids that improve the quality and durability of the printed image.
When printhead nozzles sit idle for too long (i.e., without ejecting any print fluids), nozzle issues can develop that cause some nozzles to be in a non-print-ready condition. The continued use of such nozzles can adversely impact print quality. One example of such an issue is clogs that can form in and/or over the nozzles as the print fluid dries. The degree of clogging can depend in part on the type of print fluid being ejected, and the manner by which it is ejected. For example, when exposed to high temperatures such as during ejection from a thermal inkjet printhead, latex inks can form a film on the printhead nozzle plate that results in clogging of the nozzles. Clogged nozzles can block the flow of ink, causing degradation and/or failure of the printhead and reduced overall print quality.
During printing, inkjet printing systems usually implement servicing routines that help to maintain printhead nozzles in a print-ready condition. One servicing routine often used is a process known as “spitting”, which involves the periodic ejection of printing fluid drops through the printhead nozzles.
Throughout the drawings, identical reference numbers designate similar, but not necessarily identical, elements.